Hardware Oriented Enhanced Category Determination Based on CTU Boundary Deblocking Strength Prediction for SAO in HEVC Encoder

Gaoxing CHEN
Zhenyu PEI
Zhenyu LIU
Takeshi IKENAGA

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E99-A    No.4    pp.788-797
Publication Date: 2016/04/01
Online ISSN: 1745-1337
DOI: 10.1587/transfun.E99.A.788
Type of Manuscript: PAPER
Category: Digital Signal Processing
Keyword: 
HEVC,  sample adaptive offset,  category determination,  hardware oriented,  

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Summary: 
High efficiency video coding (HEVC) is a video compression standard that outperforms the predecessor H.264/AVC by doubling the compression efficiency. To enhance the coding accuracy, HEVC adopts sample adaptive offset (SAO), which reduces the distortion of reconstructed pixels using classification based non-linear filtering. In the traditional coding tree unit (CTU) grain based VLSI encoder implementation, during the pixel classification stage, SAO cannot use the raw samples in the boundary of the current CTU because these pixels have not been processed by deblocking filter (DF). This paper proposes a hardware-oriented category determination algorithm based on estimating the deblocking strengths on CTU boundaries and selectively adopting the promising samples in these areas during SAO classification. Compared with HEVC test mode (HM11.0), experimental results indicate that the proposed method achieves an average 0.13%, 0.14%, and 0.12% BD-bitrate reduction (equivalent to 0.0055dB, 0.0058dB, and 0.0097dB increases in PSNR) in CTU sizes of 64 × 64, 32 × 32, and 16 × 16, respectively.